It is already known to grind up biological samples (tissues, cereals, hair, etc.) by enclosing the samples in test tubes that also contain micro-beads of glass, ceramics, steel, or other material, and by subjecting the hermetically sealed test tubes to essentially axial vibration at high frequency, e.g. at about 100 hertz (Hz), for a relatively short duration, of the order of 30 seconds (s) to 60 s, for example.
Various documents such as U.S. Pat. No. 5,567,050 and WO 2004/012851 describe appliances for performing such a method. They comprise a circular tray supporting the tubes and means for driving the tray with oscillatory motion about a center of rotation.
The tubes are fastened to the periphery of the tray at the same distance from the center of rotation, and they are thus moved in substantially curvilinear reciprocating motion.
Theoretically, the speed of rotation of the outlet shaft from the motor lies in the range 3000 revolutions per minute (rpm) to 8000 rpm, and the samples are subjected to linear accelerations lying in the range 150 g to 400 g in order to grind them up.
However those appliances work on a large number of samples simultaneously (in general 12, 16, 24, or 48 samples).
Those appliances are intended for large laboratories that need to analyze a large quantity of samples on a continuous basis, and generally while using the same protocol. A typical example is the laboratories that are incorporated in slaughterhouses for cattle and that serve to detect BSE. Those laboratories need to analyze a sample of the brain of each beast and to give the results of the analysis before the carcass leaves the slaughterhouse. That may represent more than 1000 analyses per day.
Many laboratories are not that specialized. They might need to grind up or stir a sample only one or two times a day or even less often, and they need to work in succession on different samples that require different protocols.
Those laboratories may also need to work on samples of different volumes, and consequently contained in test tubes of different sizes, e.g. 2 microliters (μL) and 7 μL.
For those laboratories, which are very numerous, using a 16 or 24 test-tube machine is possible, but not cost effective.